Texture Control in Hydroxyapatite by Hot Forging

Crystallographic textures of hydroxyapatite (HAp) and calcium-deficient hydroxyapatite (DAp) were controlled by hot forging. HAp, HAp-40 mass%DAp and DAp green bodies prepared by a colloidal process were hot-forged at 1273 or 1473 K, after which the c-axes of HAp and DAp with a hexagonal-based structure tended to be aligned perpendicular to the forging direction. Crystal rotation of the rod-shaped HAp and DAp during hot forging led to the texture formation, and the tendency of the texture formation enhanced with increasing forging pressure. Hot-forged HAp samples exhibited stronger texture at 1273 K than 1473 K while the texture of HAp-40 mass%DAp and DAp samples was more strongly concentrated at 1473 K. Aspect ratios of HAp and DAp, which might depend on forging temperature, was thought to strongly affect the formation of the crystallographic texture.